The present invention relates in general to a method for controlling environmental conditions to which living organisms, such as animals or plants, are exposed which employs time integrated variables (TIVs) in part to determine whether the environmental conditions should be adjusted.
Living organisms respond to multiple environmental stimuli. For example, homeothermic animals attempt to maintain some deep body set point temperature, but typically exhibit some steady periodic pattern to their environment. Since many of the environmental stimuli occur on a 24 hour repeating period, the animal's steady periodic response also behaves on the same temperature frequency pattern. An animal's capacity to integrate environmental stimuli also permits the animal to be subjected to a fairly wide range of environmental conditions, and still maintain homeostatic behavior. The wider the range of environmental conditions and the more extreme the conditions, the greater the energetic demand on the animal to maintain their homeostatic condition.
Commercial animal production is essentially all practiced based upon housing the animals under intensive conditions. An example is that of broilers in a poultry house. Maintaining an environment that is conducive for efficient animal productivity requires that the animal housing structure be equipped with a heating, cooling and ventilation system. Environmental control systems usually consist of electromechanical controls, such as thermostats, which simply activate or deactivate equipment as an inside environmental condition either exceeds or falls below some value selected by the human manager. The degree of sophistication of such systems may become increasingly complex, but essentially control still reverts to comparisons of current conditions with set point conditions.
Controllers are currently in use that are based upon microelectronics. With these, control can be based upon more than instantaneous conditions, since a microprocessor based controller has the capability to record environmental conditions in memory, and then to manipulate the stored data according to predefined algorithms to produce time integrated variables. It is typical in these controllers that independent environmental data be collected over some time interval, and then the average value of the variable over the interval is used to determine control decisions. Usually these intervals are short, on the order of milliseconds, and are simply used to provide a more stable measurement of the environmental variable. These intervals have nothing to do with the organisms whose environment is being controlled, but are simply for stability of the controller measurements. Similarly, other schemes used to achieve efficiency and control of environments strive to achieve specific target values which are determined to provide the optimum operating efficiency of the environmental control system. However, these schemes fail to take into account how the organism whose environment is being controlled, respond to the environmental variables, and thus may fail to provide the optimum environment for the organisms.
A specific problem with all prior art environmental controllers is that they do not take into account how the organism responds to the environmental conditions over time. Thus, for example, a temperature controller in a poultry house which attempts only to maintain the instantaneous temperature in the poultry house at a target value, fails to take into account how poultry respond to temperature variances over a period of time, e.g. 24 hours. The failure of the prior art controllers to take this into account results in exposure of the poultry to less than optimum conditions, which is detrimental from an economic standpoint due to less than optimum performance and health of the poultry. In addition, this often results in excessive energy usage of the environmental control devices.